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Stable chlorine isotopes are useful geochemical tracers in processes involving the formation and evolution of evaporitic halite. Halite and dissolved chloride in groundwater that has interacted with halite in arid non-marine basins has a delta Cl-37 range of 0 +/- 3 parts per thousand, far greater than the range for marine evaporites. Basins characterized by high positive (-1 to +3 parts per thousand), near-0%, and negative (-0.3 to -2.6%) are documented. Halite in weathered crusts of sedimentary rocks has delta Cl-37 values as high as +5.6 parts per thousand. Salt-excluding halophyte plants excrete salt with a delta Cl-37 range of -2.1 to -0.8%. Differentiated rock chloride sources exist, e.g. in granitoid micas, but cannot provide sufficient chloride to account for the observed data. Single-pass application of known fractionating mechanisms, equilibrium salt-crystal interaction and disequilibrium diffusive transport, cannot account for the large ranges of delta Cl-37. Cumulative fractionation as a result of multiple wetting-drying cycles in vadose playas that produce halite crusts can produce observed positive delta Cl-37 values in hundreds to thousands of cycles. Diffusive isotope fractionation as a result of multiple wetting-drying cycles operating at a spatial scale of 1-10 cm can produce high delta Cl-37 values in residual halite. Chloride in rainwater is subject to complex fractionation, but develops negative delta Cl-37 values in certain situations; such may explain halite deposits with bulk negative delta Cl-37 values. Future field studies will benefit from a better understanding of hydrology and rainwater chemistry, and systematic collection of data for both Cl and Br.

No description available.

Un des enjeux majeurs en Science de la Terre ces dernières décennies est de comprendre les interactions entre les différentes enveloppes terrestres. Le but poursuivi par ce travail est d’aborder quelques aspects de ces interactions du point de vue des cycles géochimiques des éléments volatils H2O et CO2 en se basant sur l’étude des inclusions fluides piégées dans des roches variées de la croûte terrestre, depuis sa surface jusqu’à l’interface croûte–manteau. La première partie de mon travail présente des travaux expérimentaux effectués sur de la halite. L’étude du fractionnement isotopique de l’oxygène et des cinétiques d’équilibration entre H2O et CO2 lors de l’évaporation de saumures a montré l’importance des corrections à effectuer sur les mesures isotopiques de l’oxygène pour des solutions de haute salinité. L’élaboration d’un protocole expérimental de précipitation de halite en milieu contrôlé a permis de mettre en évidence le potentiel des inclusions fluides pour les reconstitutions paléoclimatiques. La combinaison des données microthermométriques et des compositions isotopiques de l’hydrogène et de l’oxygène des inclusions aqueuses permet d’estimer les sources et la température de l’eau de formation de la halite ainsi que la vitesse du vent à l’interface eau-air pendant la croissance du cristal. Cette méthode a été ensuite appliquée aux dépôts de halite de Sicile datés du Messinien. La deuxième partie de mon travail est consacrée à l’identification des compositions chimiques et des sources des fluides circulant dans la croûte et à l’interface croûte-manteau à travers l’analyse des compositions isotopiques des inclusions fluides des granites et granulites. / One of the major challenges in Earth Sciences during the last decades has been to improve our knowledge of the interaction between the different components of the Earth System. Key aspects to improve the understanding of these processes are the acquisition of new data and the development of models to explain both mass and energy transfer between the deep and superficial components of the Earth system. The goal of this thesis is to study these transfers through the geochemical cycle of volatile elements trapped in fluid inclusions of various materials of the Earth crust. The first part of my work presents experimental study of halite. The study of oxygen isotope fractionation and equilibrium kinetics between H2O and CO2 during the evaporation of brines shows that corrections have to be made on the oxygen isotope measurements for high salinity solutions. The elaboration of an experimental protocol to form halite in controlled environment reveals the potential of fluid inclusions for palaeo climatic reconstructions. Combination of microthermometric data plus hydrogen and oxygen isotopic compositions of aqueous inclusions allows to estimate the sources and the temperature of the parental water of halite as well as the wind speed at the water-air interface during the crystal growth. This method was then applied to the Messinian halite deposits of Sicily. The second part of my work is dedicated to the identification of both the chemical compositions and the sources of fluids circulating in the crust and at the interface crustmantle through the analysis of isotopic compositions of fluid inclusions in granites and granulites.

Un des enjeux majeurs en Science de la Terre ces dernières décennies est de comprendre les interactions entre les différentes enveloppes terrestres. Le but poursuivi par ce travail est d'aborder quelques aspects de ces interactions du point de vue des cycles géochimiques des éléments volatils H2O et CO2 en se basant sur l'étude des inclusions fluides piégées dans des roches variées de la croûte terrestre, depuis sa surface jusqu'à l'interface croûte-manteau. La première partie de mon travail présente des travaux expérimentaux effectués sur de la halite. L'étude du fractionnement isotopique de l'oxygène et des cinétiques d'équilibration entre H2O et CO2 lors de l'évaporation de saumures a montré l'importance des corrections à effectuer sur les mesures isotopiques de l'oxygène pour des solutions de haute salinité. L'élaboration d'un protocole expérimental de précipitation de halite en milieu contrôlé a permis de mettre en évidence le potentiel des inclusions fluides pour les reconstitutions paléoclimatiques. La combinaison des données microthermométriques et des compositions isotopiques de l'hydrogène et de l'oxygène des inclusions aqueuses permet d'estimer les sources et la température de l'eau de formation de la halite ainsi que la vitesse du vent à l'interface eau-air pendant la croissance du cristal. Cette méthode a été ensuite appliquée aux dépôts de halite de Sicile datés du Messinien. La deuxième partie de mon travail est consacrée à l'identification des compositions chimiques et des sources des fluides circulant dans la croûte et à l'interface croûte-manteau à travers l'analyse des compositions isotopiques des inclusions fluides des granites et granulites.

In this thesis, the potential of enhanced geothermal system to provide adequate energy to a 10 MW electricity power plant from Prairie Evaporite Formation of Williston Basin was investigated. This formation partly consists of halite with low thermal resistance and high thermal conductivity, which translates into a lower drilling length to reach the desired temperature, comparing to other rock types. To this end, two numerical models with experimental data in south-west Manitoba (i.e. Tilston) and south-east Saskatchewan (i.e. Generic) were designed. The thermal reservoirs were located at 1.5 km (Tilston site) and 3 km (Generic site) with approximate thicknesses of 118 m. Considering an injection brine of 6% NaCl at 15°C, the final derived temperature at wellhead of the production wells were 43°C and 105°C respectively. Finally, the Generic site was concluded as a suitable candidate for electricity production by providing higher surfaced fluid temperature than the minimum of 80°C. / February 2017

Accumulations of brackish groundwater exist across south Louisiana within the shallow, south-dipping Pleistocene to Upper Miocene Baton Rouge Aquifer System (BRAS). This research investigates the source of brackish groundwater through geochemical analysis of representative groundwater samples by comparing the following geochemical ratios along with other trace elements. Low Bromide (Br)/Chloride (Cl) and Potassium (K) /Cl ratios, high Sodium (Na) /Cl ratios, trace Magnesium (Mg) concentrations, and low Strontium (Sr) 87/Sr86 in brackish waters from the BRAS are inconsistent with in situ saline water from marine formation fluids of similar age. The ratios are consistent with in situ saline-water sources from Lower Miocene or Paleogene formation fluids from dissolved recrystallized halite. Deep formation fluids have interacted with Louann Salt diapirs underlying the BRAS area, dissolving halite, and are shown to have moved up fault planes and entered shallow aquifers to mix with the in situ groundwaters.

Substructure dynamics incorporate all features occurring on a subgrain-scale. The substructure governs the rheology of a rock, which in turn determines how it will respond to different processes during tectonic changes. This project details an in-depth study of substructural dynamics during post-deformational annealing, using single-crystal halite as an analogue for silicate materials. The study combines three different techniques; in-situ annealing experiments conducted inside the scanning electron microscope and coupled with electron backscatter diffraction, 3D X-ray diffraction coupled with in-situ heating conducted at the European Radiation Synchrotron Facility and numerical simulation using the microstructural modelling platform Elle. The main outcome of the project is a significantly refined model for recovery at annealing temperatures below that of deformation preceding annealing. Behaviour is highly dependent on the temperature of annealing, particularly related to the activation temperature of climb and is also strongly reliant on short versus long range dislocation effects. Subgrain boundaries were categorised with regard to their behaviour during annealing, orientation and morphology and it was found that different types of boundaries have different behaviour and must be treated as such. Numerical simulation of the recovery process supported these findings, with much of the subgrain boundary behaviour reproduced with small variation to the mobilities on different rotation axes and increase of the size of the calculation area to imitate long-range dislocation effects. Dislocations were found to remain independent to much higher misorientation angles than previously thought, with simulation results indicating that change in boundary response occurs at ~7º for halite. Comparison of 2D experiments to 3D indicated that general boundary behaviour was similar within the volume and was not significantly influenced by effects from the free surface. Boundary migration, however, occurred more extensively in the 3D experiment. This difference is interpreted to be related to boundary drag on thermal grooves on the 2D experimental surface. While relative boundary mobilities will be similar, absolute values must therefore be treated with some care when using a 2D analysis. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Water and other volatiles (e.g. CO2, H2, CH4, etc.) are crucial components on Earth that ensure the habitability of the planet and play an important role in many geological processes. Small aliquots of these fluids can be preserved in the geological record as fluid inclusions and can provide valuable information about the physical and chemical environment in which they formed. The ocean is the largest water reservoir on the Earth's surface, and seawater participates in important water-rock reactions such as hydrothermal alteration of the ocean floor, a process that is currently in the spotlight for hypotheses on the origin of life, as it is an environment where generation of abiotic carbohydrates occur. The ocean chemistry varied in the geologic past to reflect major changes in the intensity of weathering, rates of midocean ridge hydrothermal discharge, changes in the climate and atmospheric CO2 concentration, and also played an important part in mass extinction events. Understanding the history of Earth's ancient oceans may hold the key to answer some of the important questions about the future of the Earth. Today, oceans hold valuable resources, such as offshore basalt formations which have been considered for submarine CO2 sequestration to mitigate greenhouse gas emissions associated with global warming. In the chapters of this dissertation, the reader will be presented with studies using fluid inclusions to advance our knowledge about the chemical evolution of seawater and reaction kinetics involving CO2, seawater and olivine – an abundant mineral in the oceanic lithosphere. Chapter I "Redox conditions in Late Permian seawater based on trace element ratios in fluid inclusions in halite from the Polish Zechstein Basin" describes application of a new redox proxy for paleo-seawater that involves analysis of redox-sensitive trace elements (e.g., Fe, Mn, U, V, Mo) in ancient seawater trapped as fluid inclusions in halite. Chapter II "Partitioning behavior of trace elements during evaporation of seawater" investigates the behavior of trace elements during the evaporation of seawater. This information is required to interpret trace element data from fluid inclusions in halite. In Chapter III "In situ monitoring of the carbonation of olivine under conditions relevant to carbon capture and storage using synthetic fluid inclusion micro-reactors: Determination of reaction rates", fluid inclusions are used as micro-reactors to monitor the reaction progress of olivine carbonation in situ and in real time at elevated temperatures (50-200 °C) and pressures using non-destructive analytical techniques such as Raman spectroscopy. / Doctor of Philosophy / Many geological processes on Earth involve water and other volatiles (e.g. CO2, H2, CH4, etc.) which are crucial components that ensure the habitability of the planet. These fluids can be preserved in the geological record in the form of fluid inclusions which are small aliquots of fluids trapped in minerals that provide information about the physical and chemical environment in which they formed. The majority of water on the Earth's surface is stored in the oceans. Seawater participates in important water-rock reactions, one of which is the hydrothermal alteration of the ocean floor. This reaction is in the spotlight currently because it represents an environment where generation of abiotic carbohydrates occur, giving rise for hypotheses about the origin of life on Earth. The chemical composition of seawater varied in the geologic past reflecting major changes in the intensity of weathering, discharge rate of midocean ridge hydrothermal systems, climate, and atmospheric CO2 concentration, and affected the survival of various marine species throughout Earth's history. For example, periodic extensions of oxygen minimum zones in the oceans played an important part in mass extinction events in the last 488 million years. Understanding the history of Earth's ancient oceans may hold the key to answer some of the important questions about the future of the Earth. Today, oceans hold valuable resources, such as offshore basalt formations which have been considered for submarine CO2 sequestration to mitigate greenhouse gas emissions associated with global warming. This dissertation explores ways to use fluid inclusions to advance our knowledge about the chemical evolution of seawater in the past and present, and the reaction of seawater with CO2 and olivine – an abundant mineral in the oceanic lithosphere – to facilitate long-term storage of CO2 in minerals to decrease the rate of global warming. Chapter I describes the application of a new redox proxy for paleo-seawater that involves analysis of redox-sensitive trace elements (elements whose solubility changes significantly as the oxidation state changes, such as Fe, Mn, U, V, Mo) in ancient seawater trapped as fluid inclusions in halite. The results suggest that trace element abundances in fluid inclusions in halite vary in response to redox changes in seawater and provide a potential redox proxy. Chapter II investigates the behavior of trace elements during the evaporation of seawater. This information is required to interpret trace element data from fluid inclusions in halite. The results of this study indicate that some elements remain in the water during evaporation of seawater (e.g. Li, B, Mo, U), while others are partially removed by precipitation of various mineral phases (e.g. Ba, Sr, Cs, Rb, Mn, V) as seawater evaporates. In Chapter III, fluid inclusions are used as micro-reactors to monitor the reaction progress of olivine carbonation in situ and in real time at elevated temperatures (50-200 °C) and pressures using non-destructive analytical techniques such as Raman spectroscopy. The results highlight that this reaction occurs rapidly, which makes it an ideal candidate for safe storage of CO2 by commercial CO2 injection projects in mafic and ultramafic rocks.

Masters of Science / This study was conducted to investigate hydrogeochemical processes controlling the evolution of groundwater chemistry and their influence on water quality in the Heuningnes Catchment. The role or influence of hydrogeochemical processes in groundwater quality in aquifer systems remains poorly understood. One of the ways of improving such understanding is to employ different techniques to explore key processes that govern groundwater quality in aquifer systems. Therefore, the present study investigated hydrogeochemical processes of groundwater resources and identified key processes that explained its quality from a spatiotemporal perspective. The quantitative approach that provides the ability to assess relationships between variables both spatially and temporally was applied. Groundwater sampling was done on four occasions during July 2017, October 2017, March 2018, and July 2018. Identification of hydrogeochemical processes controlling the evolution of groundwater chemistry and quality was done using various complementary tools. These tools included classification of the main water types, evaluation of water-rock interaction by means of stoichiometry analysis and bivariate correlation plots, inverse geochemical modelling, and statistical analysis (hierarchical cluster analysis and factor analysis). Physical parameters were measured in situ, while water samples were collected from boreholes, piezometers, springs, and artesian boreholes for laboratory analysis for major ions analysis. Descriptive and bivariate statistical methods were used to summarise and evaluate the strength of the relationship between variables, while multivariate statistical methods were applied to group similar samples based on their chemical compositions. Tri linear Piper diagrams were generated to characterize water type based on double normalizing the proportions of cations and anions, while correlation and stoichiometric analysis were applied to identify hydrogeochemical processes influencing groundwater chemistry. The results generated from the trilinear Piper diagrams confirmed the dominance of sodium and chloride ions in waters of the Heuningnes Catchment. Groundwater of a Na/Cl type is typical for a coastal aquifer characterised by saline, deep ancient groundwater. The lower parts of the Catchment were characterised by saline groundwater. The results indicated that shallow groundwater samples within the study area were more mineralised as compared to deep groundwater with EC values ranging between 20.8 and 2990 mS/m, with waters within the Table Mountain Group region (TMG), recording the lowest values. Deep groundwater for boreholes and artesian boreholes located upstream in the Catchment was fresh and yielded some of the lowest EC values recorded with an EC value below 50 mS/m. Generally, EC values increased from the upper TMG region of the Catchment towards the Bokkeveld shale region downstream and were highest during the dry season of 2018. The results indicated strong geological influences on water chemistry. Bivariate correlation and stoichiometric analysis identified cation exchange, adsorption, evaporation, weathering of carbonates, sulphates and silicate minerals as processes influencing the chemistry of groundwater in the Heuningnes Catchment. The Saturation Index (SI) results showed a change of calcite, dolomite, aragonite, gypsum, anhydrite, halite, melantinterite, siderite and sylvite from being undersaturated to oversaturated at some areas for the different seasons along the flow path. The mass-balance modelling results indicated that ion exchange and reverse ion exchange processes were more dominant at low elevations along the same flow path during the dry periods. However, at high elevations along the flow path, silicate weathering was the dominant process taking place. The findings of this study demonstrated the influence of hydrogeochemical processes in changing the water chemistry along the flow paths. In conclusion, the study showed the value of utilising various assessment tools as complementary techniques to improve the understanding about hydrogeochemical processes, and its influence on evolution of groundwater chemistry and quality. Based on the findings of the study the following recommendations were made for future studies; the sample points or sample boreholes in the study Catchment should be increased; and to have more sampling trips to enable better comparison between the possible processes